Wood preservation



May 5, 1953 E. E. PERSHALL woon PRESERVATION Filed July 16, 1951 5 wwOA MED-P mflru FZmUMul X ZNO "ZNCLZ' ENH 0.6 COMPOSITION RATIO Patented May 5, 1953 WOOD PRESERVATION Estes E. Per-shall, Hazelwood, Mo., assignor to T. J. Moss Tie Company, St. Louis, Mo., a corporation of Missouri Application July 16, 1951, Serial No. 236,994

9 Claims.

with these treating solutions are also within the scope of the present invention.

Among the several objects of this invention are the provision of treated wood materials which are resistant to fire, fungi and insects; the provision of materials of the class described which are not only initially highly resistant to fire but which retain a substantial portion of such fire resistance after extensive exposure to leaching and weathering action; the provision of treated wood materials which are free from objectionable odor, paintable and safe to handle; the provision of treating solutions for wood materials which are safe to handle and are not detrimental to the mechanical properties of the wood or the natural appearance thereof; the provision of treating solutions of the class described which are convenient to handle, economical to prepare and convenient to introduce into the material to be treated; and the provision of methods of rendering wood fire-resistant with such treating solutions which are convenient, efiicient and economical. Other features will be in part apparent and in part pointed out hereinafter.

The invention accordingly comprises the prodnets and methods hereinafter described, the scope of the invention being indicated in the following claims.

In the accompanying drawing the single figure graphically illustrates the relationship between the fire resistance both before and after leaching of the treated woods of this invention and the composition ratio of the ammoniated basic zinc chloride treating solutions at various values of retention.

Wood is a highly useful material but it possesses two inherent disadvantages, infiammability and susceptibility to deterioration by fungi and insects. Many different methods have been proposed and used to remedy one or both of these faults, but none has been completely satisfactory in providing a treated wood product which will withstand leaching to any substantial extent. Thus, the use of these prior-art treatments is limited to conditions where the treated wood is not frequently subjected to heavy rainfall, condensation or other contact with water in one form or another.

In accordance with the present invention, however, it has been found that wood products can be made which are fire-resistant (initially as well as after leaching), insect and fungi-resistant, free from objectionable odor, paintable, and safe to handle. These novel wood products contain an ammoniated basic zinc chloride distributed therethrough and are formed by impregnating wood with a treating solution of the present invention. By ammoniated basic zinc chloride is meant a composition which may include a number of compounds and not a single compound with a definite zinc to chlorine ratio.

The treating solutions described and claimed herein are not detrimental to the mechanical properties and natural appearance of the wood. These treating solutions are ammoniacal solutions of a basic zinc chloride, 1. e. complexes of zinc chloride and zinc oxide with ammonia. By basic zinc chloride, I mean a zinc chloride which has an average ratio of zinc to chlorine greater than that in zinc chloride. That is, there must be more than one atom of zinc present for each two atoms of chlorine in these ammoniated basic zinc chloride treating solutions, and the excess of zinc must be combined with oxygen or hydroxyl. Preferably, these ammoniated basic zinc chlorides have a basicity represented by a composition on the dry basis of greater than approximately .2ZnO:1ZnCl2:2NHa. By basicity is meant the amount of zinc oxide or hydroxide combined with zinc chloride. Even more preferable are ammoniated basic zinc chlorides having a composition on the dry basis between approximately .2Zn0 1ZnCl2:2NI-ls and 4Zn0 IZnClz 2NH3 and more specifically about 2ZnO 1ZnC1z12NHz particular basic zinc chloride utilized, the lower 3 is its solubility in ammonium hydroxide. It is preferred that the concentration of these basic zinc chlorides in ammonium hydroxide (on the dry basis by weight) be about 16% to 18% and that the concentration of the ammonium hydroxide be in the order of about 20% ammonia. Lower and higher concentrations of the ammoniatedbasic zinc chloride and o'fth'e ammonium hydroxide are of course within the scope or the invention.

Wood impregnated with the treating solutions of this invention is fire-resistant both before and after leaching. Fire-resistant wood is defined herein as wood which will 1osenotunorethan 55% of its weight during astandard'fire tube test (as determined by the method prescribed and approved by the United StatesZDepartment of Agriculture Forest Service, Forest Products Laboratories in Madison-,- Wisconsin, in'the'l'93l article The Fire-proofing of Wood by T. R. Truax, Senior Wood Technologist, published in the 1931 Proceedings of the Fire Protection Association). Treated wood which loses not more than 30% of its weight in this test is considered highly fire-resistant.

The degree of fire resistance of the treated wood of this invention is dependent upon such factors as the amount ahd'concentration of treating solution retained (on *a' dry basis) 'the wood-and'to some extent on the basicity of "the ammoniated basic'zinc chloride in the treating solution. Generally, the greater the amount and/or the higher the concentration of treating solution, the greater Will'be-the retention and the greater the fire resistance of the treated wood.

The concentration of the -ammoniated basic zinc chloride in the treating sol'ution will determine whether-single or multiple impregnaticns are necessary to distribute thedesired amount of ammoniated basic zinc chlorides through "the wood. For example, in relatively so'ft'woods, such as white pine, about &5 pounds of ammoniated basic zinc chloride (on the dry basis) will be retained per cubic foot-of the untreated wood after a single-impregnation if theconcentration of the ammoniated basic zinc-chleride the treating solution isa-pproximately by weight. If a-treating solution-having a lower concentration of a-mmoniated basic zinc-chloride, such as 6% to 8%, is used it maybe necessary to impregnate'the wood several times -to-obtain a retention I in-the order of 3-5 pounds percubic foot.

The fire resistance of the treated wood of this invention prior to weathering or leaching '-does not appear to be appreciably aiiected bythe basi'city of the particular ammoniated basic zinc chloridewith which -it is impregnated, but only by the amount retained. This relationship -of initial fire-tube loss to basicity "-is -illustrated in the drawing, curve -A| representing a retention of three pounds of the ammoniated basiczinc chloride treating solution on the dry basis per cubic foot of the woodtreated. Curves 13-! and C-I are similar to A-| 'but'represent-ccnstarit retentions of four and five pounds per cubic foot, respectively. 7

However, the basicity'of'the "particular ammoniated basic zinc chloride employed appears to have an effect on the degree oifire resistance of the treated wood after leaching. It .has been found that the fire-tube loss (at a constant value of retention) after leaching will vary with the basicityo-f the ammoniated ba'sic' zinc chlorides and'be an optimum "'(i. e. minimum) atayaiue .4 of about 2Zn0z1ZnClzz2NHa. This is illustrated by curves A-Z, B-2 and C-2 representing the relationship between fire-tube loss after leaching for 15 days and basicity, at three, four and five pounds per cubic foot retention, respectively. The optimum may vary somewhat depending upon the evaporation conditions.

.. wood containing'about 5i5 pounds or more of these'novel ammoniated basic zinc chlorides (on the dry basis) per cubic foot will, in general, have a fire-tube loss of about 20% or lessprior to leaching and less than 55% subsequent to leaching. If even higher degrees of fire resistance are desired greater retentions such "l5 as 14 to .lfi'p-ounds per cubic foot may be used without detriment'to the properties of the wood thus treated. -'On the other hand, wood impregnated with lesser amounts of these ammoniated basic zinc chlorides is also fire-resistant, and at retentions such as about 3.5 pounds per cubic foot, the fire-tube loss prior to leaching will not usually runmore thana'bout 30%.

' These novel treating solutionsare made in:.a'c cordance with this invention by :forming an ammoniacal solution'ofbasic zinc chloride which has an average-ratioof zinc .to chlorine greater than that in zinc chloride. Theibasiczincchloride may be formed byintermixing zinc :oxide, zinc chloride and water to form a basic zinc chloride and thereafter dissolving sit in aqueous ammonia. The amount of water intermixed with zinc chloride and zinc oxidema'y be'varied considerably without detriment totth'e -Lbasic 'zinc chloride formed. Forexample, if the amount'of water used is about --10 'of the weight :of the final zinc oxide-zinc chloride-water mixture ra cement-like form of basic Zinc chloride is formed, whereas if a higher percentage of Water such as about 25% is used, then a mud-like form #of basic zinc chloride results. If even greater amounts of water areemployed-in the water-zinc oxide-zinc chloridemixsuch as for example 50%, then a slurry-like formof basic-zinc chloride results. Alter nat'ely, zinc chloride solution or *a zinc oxideslurry may be added to -dry zinc oxide or dry zinc chloride, respectively, to form the basic zinc chlorides. Similarly, zincoxide i-n a finely ground state may be added toa hot aqueous- Zinc chloride solution which is then cooled --to form a basic'zinc'chloride precipitate. This precipitate is subsequently"dissolved in am- *monium hydroxide; *Also, zinc chloride and zinc oxide may -be intermixed with ammonium hydroxide to forman ammoniated basic :zinc chloride treating solution. The'basicity of the resulting ammoniated basic zinc chlorides may be varied by varying the ratioof zinc oxide to zinc chloride reactants.

As a further-modification ofthe method of making these'tre'ati'ng solutions, zinc chloride is mixed with ammonium hydroxide (the latter in excess over a 1:2 mole ratio of zinc chloride to ammonium hydroxide) and afixed alkali or base '(i. e. any non volatile' alkaline hydroxide such as-potassium, so'diurn-and barium hydroxides) is added to form an ammoniated basic z'inc chloride treating solutio'n. 'Ihebasic'ity'or ratio-of zinc'oxide to zinc chloride, isdependen-t upon the amount of base adde I The following --examples illustrate the inven- 't'ion.

' Example 1 An aqueous solution of approximately 'z nc cliloride by weight was heated and .zincoxide was added in a "proportion or approximately5% of the weight of the zinc chloride present in the solution. The zinc oxide-zinc chloride-water solution was then cooled and a basic zinc chloride having a composition of approximately 1ZnO:1ZnCl2:XH2O separated from the solution as a precipitate. This precipitated salt was filtered from the solution and washed with a small amount of water, and then dissolved in aqueous ammonia of approximately 25% concentration, by weight. A treating solution was made by diluting the above ammoniated basic zinc chloride solution with water until the content thereof was approximately 16-18% of ammoniated salt in 12-15% aqueous ammonia solution. The composition of this soluble ammoniated basic zinc chloride salt on a dry basis (when dried at approximately 75 C.) was approximately .75Zn: 1ZnCl2 2NH3 Example 2 15,000 grams of zinc chloride was dissolved in 10,000 milliliters of water to make a 60% solution. This solution was heated to boiling and 1,500 grams of zinc oxide was slowly added. Heating was continued until the zinc oxide was in solution. The solution was allowed to cool to room temperature. The precipitate, a basic zinc chloride, was filtered off, washed and. dissolved in 28% aqueous ammonia. A treating composition was made by diluting the above ammoniated basic zinc chloride solution with water until the content thereof was approximately 16-18% of ammoniated salt in 12-15% aqueous ammonia solution. The composition of the ammoniated basic zinc chloride salt on the dry basis (when dried at approximately 75 C.) was approximately .6ZI1OZ1Z1'1C1222NH3.

Example 3 A 50% aqueous solution of zinc chloride by weight was heated and zinc oxide was added to this solution in a proportion of approximately 5% of the weight of the zinc chloride present in the solution. This solution was then allowed to cool and a basic zinc chloride having a composition of approximately 2.5ZnO:1ZnCl2:XH2O separated from the solution as a precipitate. This basic zinc chloride salt was then dissolved in aqueous ammonia solution to give an ammoniated basic zinc chloride having a composition on a dry basis (when dried at approximately 75 C.) of approximately 1.6ZnOIlZIlC1z2NHs. A treating composition was made by diluting the above ammoniated basic zinc chloride solution with water until the content thereof was approximately 16-18% of ammoniated salt in 1215% aqueous ammonia solution.

Example 4 20 pounds of dry zinc chloride and 6.56 pounds of dry zinc oxide were intimately mixed until a smooth powder was obtained. This gave a homogeneous mixture having a molecular ratio of .55ZnOz1ZnClz. Water was added in approximately 1 pound increments until a total of 9 pounds of water had been added. The resulting mixture had the consistency of a thick mud. All large lumps formed during the addition of water were broken and dispersed so that a homogeneous mixture was obtained. The above mixture of basic zinc chloride was aged six days and then intimately mixed with 55 pounds of aqueous ammonia containing 25% ammonia by weight. The solution was then filtered to remove any undissolved solids, such as undissolved zinc oxide. The

filtrate was diluted to a strength of 16-18% solids.

Example 5 8 pounds of zinc chloride and 3 pounds of water were intimately mixed until a solution was obtained. 7.16 pounds of zinc oxide was added and the resulting cement-like mixture was mixed until a homogeneous dispersion was obtained. This gives a homogeneous mixture having a molecular ratio of 1.5ZI1O21ZI1C12. The above mixture of basic zinc chloride was intimately mixed with 40 pounds of 25% (by weight) aqueous ammonia, and the resulting solution was filtered to remove any undissolved solids, such as undissolved zinc oxide. The filtrate was diluted to a strength of 16-18% solids in 12-15% aqueous ammonia. The composition of this ammoniated basic zinc chloride solution on a dry basis (when dried at approximately 75 C.) was approximately .95ZnO lZnClz 2NH3.

Example 6 8.95 pounds of zinc oxide and 15 pounds of water were intimately mixed until a slurry was obtained. 20 pounds of zinc chloride was added and the resulting cement-like mixture was mixed until a homogeneous dispersion was obtained. The molecular ratio of this mixture was approximately .75Z1'1OZ1Z11C12. The above mixture of basic zinc chloride was intimately mixed with '70 pounds of 25% (by weight) aqueous ammonia, and the resulting solution was filtered to remove any undissolved solids, such as undissolved zinc oxide. The filtrate was diluted to a strength of 16-18% solids in 12-15% aqueous ammonia. The composition of this ammoniated basic zinc chloride solution on a dry basis (when dried at approximately 75" C.) was approximately 2385 grams of zinc oxide was placed in a ball mill and a solution of 1000 grams of zinc chloride dissolved in 1500 milliliters of water was sprayed over the zinc oxide while milling for 10 minutes. 40 pounds of commercial concentrated aqueous ammonia (28%) was added and milling was continued for another 10 minutes to dissolve the reaction product. The solution was filtered to remove any undissolved solids.

This solution contained 12.89% by weight of an ammoniated basic zinc chloride having a composition on the dry basis (when dried at approximately 75" C.) of 2.35Zn021ZnC1z22NI-Ia dissolved in ammonium hydroxide.

Example 8 A solution of 300 grams of zinc chloride dissolved in 700 milliliters of water was added to 700 milliliters of 28% aqueous ammonia. A solution of 132 grams of sodium hydroxide dissolved in milliliters of water and 150 milliliters of 28% aqueous ammonia was added to the ammoniacal zinc chloride solution to produce a treating solution of 12.1% by weight of an ammoniated basic zinc chloride having a composition on the dry basis (when dried at approximately 75 C.) of 1.5ZnO:1ZnClz:2NH3 dissolved in ammonium hydroxide.

Example 9 An aqueous solution of zinc chloride and an acetate 7 aqueous slurry of zinc' 'oxide weremixed in a tank with agitation to form a mixture containing 12 pounds of zinc oxide, -40 pounds of zinc-chloride and 60 pounds of water. The tank was sealed and this mixture was agitated for '5 days intermittently during which time-41.4 pounds of anhydrous ammonia gas was introduced intermittently to maintain an average pressure of about 50 pounds 'per square inch'and an'averag'e temperature of 85 F. The resulting solution was 39L29% by weight of an ammoniated basic'zinc chloride having a composition 'on 'a dry basis (when dried'at approximately 75 C.) of

.21ZnOf1ZnClz': ZNH:

dissolved in ammonium hydroxide.

Example-1'0 I 1895 grams of 'zincoxide wereplacedin a'ball mill and a solution of 12"75 grams zinc chloride dissolved in 1275 milliliters of water wassprayed over the zinc oxide while milling for Ill-minutes. 35 pounds of commercial concentrated aqueous ammonia were addedand milling was continued for another 10 minutes. The solution was filtered to removeany undissolved solids.

Thissolution contained 14.2% by weight of an ammoniated basic zinc chloride having a composition on the dry basis (when dried at approximate 75" -'C.) of 2.0ZnO:1ZnCl2:2NH3 dissolved in ammonium Y hydroxide.

Ezmmple 11 2390 grams of calciumhydroxide was placed in a ball mill and-a solution of 'ofldgrams of zinc chloride dissolved in .4000 milliliters of water was added while milling. A precipitate was formed, washed by decantation and filtered. 7.5 pounds of anhydrous ammonia was added to the wet filter cake (34.2 pounds). The resultant mixture was filtered to remove any undissolved solids.

This solution contained 9.6% by weight of an ammoniated basic zinc-chloride having a composition on the dry basis (when dried at approximately '75" C.) of 4.0Zn0flZnClz12NHs dissolved in ammonium'hydroxide.

li'scampl'e 12 Asample wood stick (out to the standard dimensions described and approved 'by the United States Department or Agriculture Forest Service, Forest Products Laboratories in Madison, Wiscousin, in the 1931 article The Fire-proofing of Wood, published in 1931 Proceedings of the Fire Protection Association by T. R. 'Truax, Senior Wood Technologist) was impregnated with the ammoniated basic zinc chloride'solution of Example 1 by any conventional treating apparatus until the retention was approximately 7.7 pounds of ammoniated basic zinc chloride salt per cubic foot of the. wood sample. The wood thus treated was highly fire-resistant, paintable, free from objectionable odor, possessed of desirable mechanical and chemical properties and retained a high degree of fire resistance after exposure'to leaching; Such treatedwood sample had initiall a fire-tube loss (as determined by the method described and approved by the Forest Products Laboratories in the 1931 article cited above) of approximately 17%, and after leaching the sample totally submerged in briskly running water (e. g., water is completely changed at least every 2 hours) fordays, approximately 20%. After days leaching the iire tubeloss wasonly, approximately 22%.

Example 13 Asample wood stick was impregnated with the ammoniated basic zinc chloride solution of Example 2 by any conventional treating apparatus until the retention was approximately 5 pounds of the ammoniated basic 'zinc chloride salt per cubic foot of wood. The wood thus treated was highl fire-resistant, paintable,'free from objectionable odor, possessed of desirable mechanical and chemical properties and retained a high degree of fire resistance after exposure to leaching. Such treated wood had initially a fire-tube loss of not more than 20% and after leaching totally submerged in briskly running water for 15 days. not more than 30%.

Example 14 Example 15 Asample wood stick wasimpregnated with the ammoniated basic zinc chloride solution of Example 4 by any conventional treating apparatus until the retentionwasapproximately 6.74 pounds of'ammonlated basic zinc chloride salt per cubic foot of the Wood sample. The wood thus treated was highly fire-resistant, paintable, free from objectionable odor, possessed of desirable mechanical and chemical properties and retained a high degree of fire resistance after exposure to leach: ing. Such treated wood samplev had initially a fire-tube loss of approximately 15% (as determined by the method'described and approved by the Forest Products Laboratoriesin the 1931 article cited above), and after leaching the "sample totally submerged in briskly running water for 15 days, approximately 25%.

Example 16 A sample wood stiekwas impregnated with the ammoniated basic zinc chloride solution of Example 5 by any conventional treating apparatus until the retention was approximately 5x6pounds'of the ammoniated basic zinc chloride salt per cubic foot of wood. The wood thus treated was highly fire-resistant, paintable, 'free from objectionable odor, possessed of desirable mechanical and chemical properties and retained a high degree of fire resistance after exposure to leaching. -'Such treated wood has initially "a fire-tube loss of approximately -20% and after leaching in running water for 15 days,-approximately 27%. -Af-ter30 days leaching the fire-tube loss was only 30% Example 17 A sample wood stick was impregnated-with' the ammoniated basic zinc chloride composition of Example 6 until "the retention was approximately 5.3 pounds of ammoniated salt per cubicJfo'ot of wood-sample. The wood thus-treated was highly fire-resistant, paintable, free from objectionable odor, possessed-cf desirable mechanical and chemical properties andretained ahigh. degree 'o'frfire resistance after exposure to leaching. :SllUh .9 treated wood had initially a fire-tube loss of approximately 20% and after leaching in running water for 15 days approximately 29%.

Example 18 The procedure of Example 12 was followed using the treating solution of Example 7. The characteristics of the treated wood stick were similar to those described in Example 12 except that at a retention of 5.5 pounds per cubic foot the initial fire-tube loss was 17% and after 15 days of leaching it was 22%.

Example 19 The procedure of Example 12 was followed using the treating solution of Example 8. The characteristics of the treated wood stick were similar to those described in Example 12 except that at a retention of pounds per cubic foot the initial fire-tube loss was 20% and after days of leaching it was 32%.

Example The procedure of Example 12 was followed using the treating solution of Example 9. The characteristics of the treated wood stick were similar to those described in Example 12 except that at a retention of 4.3 pounds per cubic foot the initial fire-tube loss was 19% and after 15 days of leaching it was 48%.

Example 21 The procedure of Example 12 was followed using the treating solution of Example 10. The characteristics of the treated wood stick were similar to those described in Example 12 except that at a retention of 5.2 pounds per cubic foot the initial fire-tube loss was 18% and after 15 days of leaching it was Example 22 The procedure of Example 12 was followed using the treating solution of Example 11. The characteristics of the treated wood stick were similar to those described in Example 12 except that at a retention of 8 pounds per cubic foot the initial fire-tube loss was 18% and after 15 days of leaching it was 23% Any customary method of impregnation may be employed for treating wood with the treating solutions of the present invention.

It is to be understood that in addition to the ratio of ZnO to ZnClz in the above compositions being variable as stated, variations in the conditions of evaporation of the treating solution to a dry basis will vary the ratio of NH3 to ZnClz.

It is also to be understood that ammoniated basic zinc chlorides having higher ratios than 4ZnOIlZnCl2Z2Nh3, such as 7ZnO21ZnC12Z2NI-I3 and 10ZnOz1ZnChz2NI-Iz, have been made and used successfully in carrying out the present invention.

In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained.

As many changes could be made in the above methods and products without departing from the scope of the invention, it is intended that all matter contained in the above description shall be interpreted as illustrative and not in a limiting sense.

I claim:

1. A treating solution for rendering wood fire- 10 resistant before and after leaching with water comprising an ammoniacal solution of an ammoniated basic zinc chloride having a composition on the dry basis between approximately 2. A treating solution for rendering wood fireresistant before and after leaching with water comprising an ammonical solution of an ammoniated basic zinc chloride having a composition on the dry basis of approximately 3. A treating solution for rendering wood fireresistant before and after leaching with water comprising an ammoniacal solution of an ammoniated basic zinc chloride having a composi-- tion on the dry basis between approximately .2ZnO:1ZnClz:2NI-I3 and 4ZnOzlZnChz2NHs, the concentration of said ammoniated basic zinc chloride in said solution being at least approximately 10% by weight.

4. A treating solution for rendering wood fireresistant before and after leaching with water comprising an ammoniacal solution of an ammoniated basic zinc chloride having a composition on the dry basis between approximately .2ZnOz1ZnClzr2NHa, and 4ZnO:1ZnCl2:2NH3, the concentration of said ammoniated basic zinc chloride in said solution being at least approximately 16% to 18%.

5. A treating solution for rendering wood fireresistant before and after leaching with water comprising an ammoniacal solution of an ammoniated basic zinc chloride having a composition on the dry basis of approximately the concentration of said ammoniated basic zinc chloride in said solution being approximately 16% to 18% in approximately 20% ammonium hydroxide.

6. Wood which is fire-resistant before and after leaching with water comprising the product resulting from the impregnation and drying of wood with an ammoniacal solution of an ammoniated basic zinc chloride having a composition on the dry basis between approximately and approximately 4Zn0: 1ZnC12 2NH3.

'7. Wood which is fire-resistant before and after leaching with water comprising the product resulting from the impregnation and drying of wood with an ammoniacal solution of an ammoniated basic zinc chloride having a composition on the dry basis of approximately 8. Wood which is fire-resistant before and after leaching with water comprising the product resulting from the impregnation and drying of wood with an ammoniacal solution of an ammoniated basic zinc chloride to obtain a retention of at least approximately 3.5 pounds per cubic foot on the dry basis, said ammoniated basic zinc chloride having a composition on the dry basis between approximately .2ZnOz1ZnC1zz2NHs and approximately 4ZnO: 1ZnC1z 2Nm.

9. Wood which is fire-resistant before and after leaching with water comprising the product resulting from the impregnation and drying of wood with an ammoniacal solution of an am mes-mam.

1-2 .moniated' basic: zinechlorideto obtain a reten Number Name Date tion of at least approximately 5.5. pounds" per' 1,261,736 Ferguson 1 Apr: 2,1913 cubic foot onthe dry: basis, said ammoniated: 1,318,524 Arent'et-al. Oct. 1'1',;1El19 basic zinc chloride having. wcompusition on the 1,338,322 Munroe Apr. 27, 1920 dry basis of approximately. 22:10.: 1ZnC1z:2NI-Is. 5

ESTESE PERSHALL. 7 OTHER REFERENCES 7 Me11or'"ComprehensiveTreatise on Inorganic References Cited the file of: this patentand Theoretica1- Chemistry"Longmams',v Green UNITEDSTATES Pnmms and"Co. --London-1929'Vo1; 4; pages 545,. 546

' andt549. Number. Name Date 959L505 G'erlache May 31", 1910 

1. A TREATING SOLUTION FOR RENDERING WOOD FIRERESISTANT BEFORE AND AFTER LEACHING WITH WATER COMPRISING AN AMMONIACAL SOLUTION OF AN AMMONIATED BASIC ZINC CHLORIDE HAVING A COMPOSITION ON THE DRY BASIS BETWEEN APPROXIMATELY
 6. WOOD WHICH IS FIRE-RESISTANT BEFORE AND AFTER LEACHING WITH WATER COMPRISING THE PRODUCT RESULTING FROM THE IMPREGNATION AND DRYING OF WOOD WITH AN AMMONIACAL SOLUTION OF AN AMMONIATED BASIC ZINC CHLORIDE HAVING A COMPOSITION ON THE DRY BASIS BETWEEN APPROXIMATELY 